1. Technical Field
The present invention relates to an electronically controlled mechanical timepiece enabled to accurately drive time display instruments, such as hands, by using a generator to convert mechanical energy of a mechanical energy source, such as a spring, into electrical energy, and controlling the rotation cycle of the generator by operating a rotation control device by the electrical energy. The present invention also relates to a control method therefor. More particularly, the present invention relates to an electronically controlled mechanical timepiece enabled to reliably perform rate measurement, and a control method therefor.
2. Background Art
Electrical controlled mechanical timepieces described in Japanese Examined Patent Publication No. 7-119812 Official Gazette and Japanese Unexamined Patent Publication No. 8-50186 Official Gazettes are known as those each enabled to accurately drive hands fixed to a wheel train and to indicate time by using a generator to convert mechanical energy in an unwinding mode of a spring into electrical energy, and operating a rotation control device by the electrical energy to control the value of electric current flowing through a coil of the generator
Meanwhile, in the case of an ordinary quartz timepiece driven by a button-type battery and a timepiece adapted to move hands by driving a motor by using electric power generated by the generator that is driven by a oscillating weight, rate measurement is performed by feeding electric current through a coil of the motor so as to measure the accuracy of the timepiece, and by receiving leakage magnetic flux generated at that time by a rate measuring device.
However, the electronically controlled mechanical timepiece has no motor for moving hands, so that rate measurement utilizing a motor cannot be performed. Applicants of the present application, thus, considered that another coil for rate measurement was provided therein. However, in this case, such a timepiece has drawbacks in that the size thereof is large and that the cost thereof increases.
A first object of the present invention is to provide an electronically controlled mechanical timepiece, which can perform rate measurement and reduce the size thereof and decrease the cost thereof, and to provide a control method therefor.
Further, in a conventional electronically controlled mechanical timepiece, a rotation control device constituted by ICs is operated by rectifying an AC output of a generator to direct current through a rectifier circuit. In such a case, usually, a bridge rectifier circuit using 4 diodes is used as the rectifier circuit. However, in such a bridge circuit, the diodes consume considerable electric power. Thus, the conventional electronically controlled mechanical timepiece has a drawback in that such a bridge circuit is unsuitable for a rectifier circuit to be used to rectify an AC output of a generator, which can generate only a small amount of electric power and is provided in a device, such as a timepiece.
To eliminate the drawbacks, the applicants of the present application developed a rectifier circuit that was suitable for an electronically controlled mechanical timepiece and that has first and second switches, each of which is provided between a corresponding one of two output terminals of a generator and a power storage device and is controlled according to the polarity of (or voltage level at) a corresponding one of the output terminals of the generator so that when one of the switches is closed, the other switch is opened, and the boosting can be performed by intermittently closing the opened switch at short time intervals, namely, by chopping.
When both the first and second switches are closed (namely, turned on) in this rectifier circuit, the AC output terminals of the generator are short-circuited. Thus, when each of the switches is turned on, short braking is caused in the generator. Moreover, energy is stored in the coil of the generator. Further, when one of the switches is opened (namely, turned off), the generator operates, and the energy stored in the coil results in an increase in the electromotive force or voltage.
Thus, the voltage level of an output signal at each of the AC output terminals can be raised. The output voltage of the rectifier circuit can be increased for that, as compared with the case that no chopping is performed. Consequently, the charging voltage in the case of charging a capacitor can be enhanced.
However, the electronically controlled mechanical timepiece, in which such a chopping rectifier circuit is incorporated, has another drawback in that although the charging efficiency is increased, rate measurement for checking the accuracy of the timepiece is difficult to perform.
That is, in the electronically controlled mechanical timepiece, the hands are operated in synchronization with the rotation of the rotor of the generator. It is, thus, considered that the rate measurement is performed by detecting magnetic variation caused by the rotation of the rotor.
However, in the electronically controlled mechanical timepiece, which undergoes a chopping control operation, a rate measurement device detects a chopping signal, which is generated by chopping, in addition to a magnetic variation signal generated by the rotation of the rotor. This presents the additional drawback in that the accurate rate measurement is difficult to perform.
A second object of the present invention is to provide an electronically controlled mechanical timepiece, which undergoes a chopping control operation and can easily perform rate measurement, and a control method therefor.
According to the present invention, there is provided an electronically controlled mechanical timepiece having a mechanical energy source, a generator, driven by the mechanical energy source, for generating an induced electromotive force and supplying electrical energy, a power supply circuit, into which the electrical energy is charged, and a rotation control device, driven by this power supply circuit, for controlling a rotation cycle of the generator. In this timepiece, a coil of the generator is used as a rate measuring coil.
When the coil of the generator is used as the rate measuring coil, there is no need to provide an additional rate measuring coil in the electronically controlled mechanical timepiece that has no motor for driving a time display device, such as hands, in addition to the generator. Thus, as compared with the case in which the rate measuring coil is added, the size of the electronically controlled mechanical timepiece can be reduced. Moreover, the cost thereof can be decreased.
At that time, preferably, the rotation control device ceases the power generation operation of the generator, for the predetermined time, by stopping the operation of controlling the rotation of the generator at constant cycles. Moreover, during that, the rate measurement is performed by feeding electric current from the power supply circuit through the coil of the generator.
With such a configuration, when the rate is measured, actually, leakage magnetic flux, which would be caused by performing an ordinary rotation control operation of the generator, is not generated. Only leakage flux for measuring the rate is generated by feeding electric current in the coil of the generator. Thus, the signal can be reliably and easily detected by a rate measuring device. The rate-measuring accuracy can be improved.
Further, the electronically controlled mechanical timepiece may have a first switch disposed between a first input terminal of the power supply circuit and a first output terminal of the generator, a second switch disposed between the first input terminal of the power supply circuit and a second output terminal of the generator, a third switch disposed between a second input terminal of the power supply circuit and the output terminal of the generator, and a brake control circuit enabled to control the switches independent of one another.
The electronically controlled mechanical timepiece of the present invention drives the hands and the generator by using the mechanical energy source, such as a spring. The number of rotations of the rotor, thus, that of rotation of each of the hands is controlled by applying a brake to the generator by using the brake control circuit of the rotation control device. At that time, in a state in which one of the first and second switches is closed, the brake control circuit performs the chopping control of the generator by opening and closing the other switch.
Incidentally, the brake control circuit can control the respective switches independent of each other. Thus, at constant cycles (for instance, at 1 second intervals), the second and third switches are closed for a predetermined time (for example, about 1 msec), and the first switch is opened (namely, turned off). Electric current is fed from the power supply circuit through the second and third switches into the coil of the generator by controlling the switches in this way. The rate measurement can be performed by measuring rate measuring pulses by means of a magnetic sensor of the rate measuring device in response to a change in a magnetic field generated by the coil when the electric current flows therethrough.
These rate measuring pulses correspond to the magnetic field generated by the electric current flowing through the coil in a short time. That is, these pulses are signals generated by an abrupt change in the electric current. Therefore, these pulses can be easily distinguished from the chopping signal. Consequently, the rate measurement can be reliably performed.
Incidentally, the first switch may comprise a first field effect transistor having a gate connected to the second output terminal of the generator, and a second field effect transistor connected in parallel with this first field effect transistor and adapted to be turned on and off by the brake control circuit. Moreover, the second switch may comprise a third field effect transistor having a gate connected to the first output terminal of the generator, and a fourth field effect transistor connected in parallel with this third field effect transistor and adapted to be turned on and off by the brake control circuit.
With such a configuration, for example, when the polarity at the first output terminal of the generator is positive (+), and the polarity at the second output terminal thereof is negative ((xe2x88x92), the electric potential is lower than that at the first output terminal), the first field effect transistor (in the case of Pch) having a gate connected to the second output terminal is in an on-state, while the third field effect transistor (in the case of Pch) having a gate connected to the first output terminal is in an off-state. Thus, an AC output signal outputted from the generator flows through a path from the first output terminal through the first field effect transistor, the power storage device, such as a capacitor, and the second AC output terminal. Consequently, the AC output signal is rectified.
Moreover, when the polarity at the second output terminal is positive, and the polarity at the first output terminal is negative (that is, lower in the electric potential than the level at the second output terminal), the third field effect transistor having a gate connected to the first output terminal is in an on-state, while the first field effect transistor having a gate connected to the second output terminal is in an off-state. Thus, the output signal is caused to flow in a path from the second output terminal, through the third field effect transistor, the power storage device, such as a capacitor, to the first output terminal.
At that time, each of the second and fourth field effect transistors is repeatedly turned on and off in response to the input of the chopping signals to the gate thereof. Moreover, the second and fourth field effect transistors are connected in parallel with the first and third field effect transistors. Thus, when the first and third field effect transistors are in an on-state, electric current flows therethrough regardless of the on-state and the off-state. However, when the first and third field effect transistors are in an off-state, electric current flows therethrough if the second and fourth field effect transistors are turned on by the chopping signals. Therefore, when the second and fourth field effect transistors are connected in parallel with one of the first and third field effect transistors, which are in an off-state, are turned on by a chopping signal, both the first and second switches are in an on-state. Thus, a closed loop is established among the AC output terminals. Incidentally, this closed loop may be constituted by connecting the AC output terminals through resistors. However, preferably, the closed loop is constituted by directly short-circuiting the AC output terminals. In the case that a resistor is interposed between the terminals, there is a concern that the output terminals are not close to the same potential at some resistance value, and that thus, no rate measuring pulses are outputted. However, the terminals can be reliably put at the same potential by short-circuiting the terminals. Thus, the rate measuring pulses can be reliably outputted.
Consequently, the voltage level of the AC output signal can be enhanced by chopping. A rectification control operation is performed in the first and third field effect transistors each having a gate connected to the AC output terminal. Thus, there is no necessity for using comparators. The configuration of the timepiece is simplified, so that the number of components is decreased. Moreover, the charging efficiency can be prevented from being lowered owing to the power consumption of the comparators. Furthermore, the turning-on or turning-off of the first and third field effect transistors is controlled by utilizing the voltage of the AC output terminal. Therefore, each of the field effect transistors is controlled in synchronization with the polarities at the AC output terminals. Consequently, the rectification efficiency can be enhanced.
Further, the electronically controlled mechanical timepiece may be configured so that a boosting circuit is connected to the third switch, and that when the third switch is closed, electric current boosted by the boosting circuit is supplied to the coil of the generator.
When the voltage level of the current signal flowing in the coil at the time of closing the third switch is raised to a high level by connecting the boosting circuit in series with the third switch, the signal level of the rate measuring pulses can be made to be considerably higher than that of the chopping signal. Thus, the rate measuring pulse can be more easily detected. Furthermore, the rate measurement can be more easily achieved.
Furthermore, preferably, the brake control circuit is adapted to open the first switch and close the third switch for a predetermined time (namely, a second set time), at constant cycles (for instance, 1 to 2 seconds), after establishing a closed loop among the output terminals of the generator by closing the first and second switches for a predetermined time (namely, a first set time).
Thus, even after the chopping control is canceled, electric current can be made to flow through the coil of the generator and rate measuring pulses can be outputted by opening the first switch and closing the third switch after the switches are once closed, so that short braking is applied by establishing a closed loop by short-circuiting the output terminals of the generator. Consequently, the rate measuring pulses are not superposed on the chopping signals. The rate measuring pulses can be reliably and easily detected.
Moreover, in the case that the switches are the first to fourth field effect transistors, preferably, the brake control circuit is adapted to turn off the second transistor and turn on the third transistor for a predetermined time (namely, a second set time), at constant cycles (for example, 1 to 2 seconds), after establishing a closed loop among the output terminals of the generator by turning on the second and fourth transistors for a predetermined time (namely, a first set time).
In the case that the second and fourth field effect transistors are controlled by the brake control circuit in this way in such a manner as to be simultaneously turned on, so that short braking is caused in the generator, the output terminals of the generator are at the same potential. Therefore, sufficient potential for turning on the transistors is not applied to the gates of the first and second transistors. Consequently, both the first and third transistors are turned off. Thus, the operations of the first and third transistors controlled in synchronization with the output terminal voltage of the generator are canceled by controlling the second and fourth transistors. Thereafter, the brake control circuit controls the on/off of the second and fourth transistors, so that the closing/opening of the first and second switches can be reliably controlled. Thus, the rate measuring pulses can be reliably outputted by controlling the third switch together therewith.
Incidentally, the brake control circuit may control the operation of the third switch only in the rate measuring mode that is set by putting in and pulling out the winding crown several times. Alternatively, the circuit may control the third switch during a steady operation thereof. Even when the third switch is operated during the steady operation, the time period (namely, the second set time), in which the third switch is closed, is very short. Thus, the rate measurement can be achieved without affecting the speed-governing control.
Further, in the electronically controlled mechanical timepiece, the brake control circuit may be adapted to be able to switch between a rate measuring mode and a hand moving mode, and adapted to establish a closed loop among the output terminals of the generator by turning on the second and fourth transistors for a predetermined time after canceling brake control applied to the generator by turning off the second and fourth field effect transistors for a predetermined time, and adapted to subsequently turn off the second transistor and close the third switch for a predetermined time.
Thus, the rate measuring mode is established in the timepiece. Then, the brake control of the generator is canceled, so that the generator is brought into a free running state. Subsequently, the rate measuring pulses are outputted. Consequently, no chopping signals are outputted in the rate measuring mode by performing the chopping control. Thus, the rate measuring pulses can be reliably detected. Moreover, the generator continues to operate, so that the charging of the power supply circuit can be continued even in the case that the rate measurement is performed for a long time. Furthermore, as a result of providing the rate measuring mode, the time period, in which the third switch is controlled, is limited to the rate measuring mode. In the hand moving mode, only the speed-governing control operation is performed. Thus, the speed-governing control operation can be efficiently performed. Moreover, the current consumption can be reduced by closing the third switch.
Moreover, preferably, the time period, during which a closed loop is formed among the output terminals of the generator, that is, the predetermined time (namely, the first set time), during which the first and second switches are closed, or the predetermined time (namely, the first set time), during which the second and fourth transistors are turned on, is set in such a manner as to be longer than a mask time, namely, a time period, in which the next magnetic pulse should not be detected, to be set when a magnetic pulse is inputted in a rate measuring device (namely, a quartz tester). Incidentally, the mask time is usually set at 70 to 80 msec (milliseconds), so that the predetermined time (namely, the first set time) is set at, for instance, a value, which is equal to or more than 70 msec and equal to or less than 200 msec, preferably, equal to or more than 80 msec (for example, 125 msec).
When a closed loop is formed among the output terminals of the generator by connecting the first and second switches or turning on the second and fourth transistors, magnetic pulses based on a change in the magnetic flux is generated in the case that the electromotive voltage at each of the output terminals is equal to or more than a predetermined value. The rate measuring device sets a predetermined time (for example, about 80 msec) and another predetermined time (namely, the mask time), in which the detection of magnetic pulses is not performed, when a magnetic pulse is inputted thereto, so as to prevent an erroneous detection due to external disturbance and to stably detect magnetic pulses. Therefore, in the case that the moment, at which an actual rate measuring pulse is generated, namely, the moment when the first switch is opened and the third switch is closed, or when the second transistor is turned off and the third switch is closed, is within the mask time, no rate measuring magnetic pulse is detected. In contrast, in the case that the time (namely, the first set time), in which a closed loop is established among the output terminals of the generator as described above, is set in such a way as to be longer than the mask time, the mask state is canceled when the closed-loop state is canceled and the third switch is closed and the rate measuring pulses are outputted. Thus, the rate measuring pulses can be reliably detected. Even when magnetic pulses other than the rate measuring pulses are outputted, the rate measurement can be reliably performed.
Incidentally, a very short time, for example, 0.2 to 1.0 msec or so is sufficient for the time (namely, the second set time), during which the third switch is closed, When this time period is short, an amount of electric current, which flows from the power storage device through the third switch and has an amount proportional to this time period, can be reduced.
Incidentally, it is preferable that the constant cycle, in which a closed loop is formed among the output terminals of the generator, is, for instance, 1 to 2 seconds. In the case that a light emitting diode (LED) adapted to blink at the time of detecting a magnetic pulse is provided in the rate measuring device, and that the constant cycle is 1 to 2 seconds, the LED also blinks at 1 to 2 second intervals. Thus, it is easy for an observer to check an operating state.
Further, preferably, the rotation control device is adapted to open the second switch or turn off the fourth transistor after a predetermined time (namely, a third set time), which is shorter than a mask time set when a magnetic pulse is inputted in the rate measuring device, elapses since the third switch is closed. This third set time is set at a value, which is, for instance, equal to or more than 60 msec and equal to or less than 90 msec, preferably, within a range of about 60 to 70 msec.
When the second switch is opened or the fourth transistor is turned off, a magnetic pulse is generated in the case that the electromotive voltage at the output terminal of the generator is equal to or more than the predetermined value. At that time, in the case that the moment, at which this magnetic pulse is generated, since the generation of the rate measuring pulse is set in such a manner as to be within the mask time, this magnetic pulse is not detected. Consequently, the rate measurement can be reliably performed.
Furthermore, the electronically controlled mechanical timepiece according to the present invention may be configured so that the rotation control device has a rotation stopping device for mechanically stopping a rotation of the generator, and that the operating mode is able to switch between a rate measuring mode and a hand moving mode, and that the first switch is opened and the second switch is closed and the third switch is closed for a predetermined time, in a rate measuring mode, after the rotation stopping device stops rotation of the generator.
In the case that the rotation control device has a rotation stopping device, the rate measurement can be performed by closing the third switch in a state, in which the rotation of the rotor is stopped. In this case, the rotor stops. Thus, there is no need for the chopping control. The timepiece is configured so that when the rate measurement is performed, only the rate measurement pulses are outputted. Consequently, the rate measurement is more reliably performed.
Further, according to the present invention, there is provided a method for controlling an electronically controlled mechanical timepiece having a mechanical energy source, a generator, driven by the mechanical energy source, for generating an induced electromotive force and supplying electrical energy, a power supply circuit, into which the electrical energy is charged, and a rotation control device, driven by this power supply circuit, for controlling a rotation cycle of the generator. In the case of this method, rate measurement is performed by feeding electric current through a coil of the generator at constant cycles.
According to such a method of the present invention, the rate measurement can be performed by feeding the electric current in the coil of the generator. Thus, there is no necessity for adding a rate measuring coil in the timepiece. Consequently, the size of the electronically controlled mechanical timepiece can be reduced. Moreover, the cost thereof can be decreased.
At that time, preferably, an operation of controlling a rotation of the generator is stopped at constant cycles. Furthermore, when the operation of controlling the rotation of the generator is stopped, rate measurement is performed by feeding electric current through the coil of the generator.
According to such a control method, the rate measurement is performed by feeding electric current in the coil of the generator when the rotation control operation of the generator is stopped. Thus, a signal caused by the rotation control of the generator is not superposed on a hand moving signal, such as leakage flux at the time of rate measurement. Consequently, the rate measurement can be reliably and easily performed.
Moreover, the method for controlling an electronically controlled mechanical timepiece may be adapted so that the timepiece further comprises a first switch disposed between a first input terminal of the power supply circuit and a first output terminal of the generator, a second switch disposed between the first input terminal of the power supply circuit and a second output terminal of the generator, and a third switch disposed between a second input terminal of the power supply circuit and the output terminal of the generator, and that the brake control circuit opens the first switch and closes the third switch for a predetermined time, at constant cycles, after establishing a closed loop among the output terminals of the generator by closing the first and second switches for a predetermined time.
Furthermore, the method for controlling an electronically controlled mechanical timepiece may be adapted so that the brake control circuit is adapted to be able to switch between a rate measuring mode and a hand moving mode, and adapted to establish a closed loop among the output terminals of the generator by turning on the second and fourth transistors for a predetermined time after canceling brake control applied to the generator by turning off the second and fourth field effect transistors for a predetermined time, and adapted to subsequently turn off the second transistor and close the third switch for a predetermined time.
Further, the method for controlling an electronically controlled mechanical timepiece may be adapted so that the brake control circuit is adapted to be able to switch between a rate measuring mode and a hand moving mode. In the rate measuring mode, after the rotation of the rotor of the generator is stopped by the rotation stopping device, at constant cycles, the first switch is opened, and the second and third switches are closed for a predetermined time, so that electric current is fed from the power supply circuit through the coil of the generator for the predetermined time.
According to each of these control methods, electric current can be fed from the power supply circuit through the coil of the generator, and a rate measuring pulse can be outputted by controlling each of the switches. Thus, the rate measurement can be reliably performed.
Furthermore, in the case that the rate measuring mode is provided therein, each of the switches can be controlled in such a way as to facilitate the rate measurement in the rate measuring mode. Thus, the rate measurement can be performed more easily and reliably.